The use of gas-filled pressurised balloons to station diverse telecommunications and/or surveillance platforms in the stratosphere is known, for example, from U.S. Pat. No. 5,104,059. One particular problem of such pressurised balloons arises from the variations in temperature to which they are exposed, firstly throughout the day and secondly at night. In the daytime, the balloon's surface is exposed to direct solar radiation, and the gas in the balloon's interior is heated by the solar radiation, causing the gas pressure to rise. At night, on the other hand, both ambient and gas temperatures fall and therefore also the gas pressure in the pressurised balloon. This imposes even more demands on the material and the construction of the pressurised balloon. It also makes it more difficult to maintain the platform's altitude and position with respect to the earth.